We propose a combined genetic and biochemical approach to the study of eukaryotic protein synthesis. Methods will be developed for the selection of a wide variety of antibiotic resistant and conditionally lethal (ts) mutants of Chinese hamster cells altered in soluble, ribosomal, and regulatory elements of mammalian protein synthesis. Biochemical characterization of these mutants should promote understanding of the mechanism of protein synthesis. Structure-function relationships of ribosomal proteins will be determined by the biochemical and immunologic characterization of wild type and mutant ribosomes. Methods will be developed for the production of monoclonal antibodies to be used for immunologic characterization of ribosomal protein function. The mutants selected will be used as genetic markers to determine the genetic organization and expression of genes coding for protein synthesis components in mammalian cells.